1. Field of the Invention
The invention relates to a high fidelity audio amplifier which uses a new structure of combinated feedback composed by feedforward error correction and a negative feedback loop.
The invention develops a new structure of the feedback loops that can be used in an audio amplifier in order to improve performances using the advantages offered by feedforward error correction and negative feedback, both patented by H. S. Black, U.S. Pat. No. 2,102,671 and U.S. Pat. No. 1,686,792.
2. Description of the Prior Art
There have been made advances in the past years in the design of high fidelity audio frequency amplifiers but with new improvements new flaws are discovered.
The negative feedback largely used in audio frequency amplifiers, next to the indisputable advantages it offers (reduces distortions, increases the bandwidth, controls the amplifier response, etc.) has some disadvantages too (cannot minimize the distortions, can generate instability, decreases the overall gain, etc.
The feedforward error correction mainly allows cancelation of errors, i.e. distortion introduced by the amplifier in terms of stability and doesn't present a feedback loop that might leads to instability.
The invention try to solve another problems of a conventional amplifier i.e. poor linearity of the output power stage characteristics, poor thermal stability of the conventional output class AB stages, by using a class B output stage, without quiescent current, controlled by the combined feedback, the clean feedback.
Using combined feedback, the voltage distortion of the amplifier can be effectively improved by the negative feedback loop in the high frequency regions.
The object of this invention is to provide a new structure of the feedback loops which allow to obtain a simple, but high performance audio amplifier in terms of stability, low harmonic and intermodulation distortion, excellent dynamic performance and above all outstanding sonic performance.